What did you do to actually count trees? Even from aerial Lidar it can be a bit finicky for closed canopies.
Here is the first pass, https://i.imgur.com/f7Gpxmm.png, it under counted and also even counted my house as a tree, lol.
Even the more sophisticated algorithms pretty much always do this ;-)
You are probably not interested in taking this further, but you could give the Li tree filter a try: https://pdal.org/en/stable/stages/filters.litree.html
But getting perfect segmentation is basically impossible.
What did you do to actually count trees? Even from aerial Lidar it can be a bit finicky for closed canopies.